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Electric Motor

An electric motor is a device that converts electrical energy into mechanical energy by using the force on a current-carrying coil in a magnetic field.

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Student-friendly explanation

When current flows through the coil of a motor placed in a magnetic field, forces act on the two sides of the coil in opposite directions. These forces create a turning effect, so the coil rotates. The split-ring commutator helps keep the coil rotating in the same direction. Motors are used in fans, mixers, washing machines, and many other appliances.

How to write this in exams

  1. 1

    Start with the exact idea

    An electric motor is a device that converts electrical energy into mechanical energy by using the force on a current-carrying coil in a magnetic field.

  2. 2

    Then show how to use it

    1. Place a coil between magnet poles. 2. Pass current through the coil. 3. Forces act on opposite sides of the coil. 4. Coil rotates. 5. Commutator reverses current every half turn to keep rotation going.

  3. 3

    Add one concrete example

    A ceiling fan works because an electric motor rotates its blades when current passes through the coil system inside it.

  4. 4

    Avoid this incomplete answer

    A common wrong answer is that the coil rotates because it is simply heated or pushed by the battery. The real cause is magnetic force on current-carrying sides of the coil.

Definition

An electric motor is a device that converts electrical energy into mechanical energy by using the force on a current-carrying coil in a magnetic field.

Example

A ceiling fan works because an electric motor rotates its blades when current passes through the coil system inside it.

Rule to remember

Motor action depends on force on a current-carrying conductor in a magnetic field, explained by Fleming's left hand rule.

Memory hook

Motor means current becomes motion.

Examples and method

Worked example

If a small motor coil is connected to a battery, one side of the coil moves upward and the other downward due to magnetic force. After half a turn, the commutator reverses current so the coil keeps turning.

Method to apply

1. Place a coil between magnet poles. 2. Pass current through the coil. 3. Forces act on opposite sides of the coil. 4. Coil rotates. 5. Commutator reverses current every half turn to keep rotation going.

Diagram support

Draw a rectangular coil between magnet poles, split-ring commutator, brushes, and battery connections with rotation arrows.

How CBSE asks it

Explain working of an electric motor, label its parts, or state the role of the commutator.

Avoid common mistakes

Common confusion

Students often say the motor itself produces electricity. In fact, it uses electricity to produce motion.

Common wrong answer

A common wrong answer is that the coil rotates because it is simply heated or pushed by the battery. The real cause is magnetic force on current-carrying sides of the coil.

Exam tip

In answers, mention the rotating coil, magnetic field, and commutator together for full marks.

Quick check

Why does the coil in an electric motor keep rotating instead of stopping after one push?

The split-ring commutator reverses the current after every half turn, so the force on the coil keeps producing rotation in the same direction. This is why the motor continues to spin.

Study the electric motor diagram carefully

Use the labelled diagram to keep electric motor clear in short answers and revision.

What this diagram makes clear

This diagram keeps the labels and direction of electric motor in the right order.

Where this helps in exams

Use this for labelled diagram work and short exam answers on electric motor.

Revision cue

Revise electric motor through the labels before writing the answer.

Answer writing and exam use

1-mark answer

An electric motor is a device that converts electrical energy into mechanical energy by using the force on a current-carrying coil in a magnetic field.

2-mark answer

An electric motor is a device that converts electrical energy into mechanical energy by using the force on a current-carrying coil in a magnetic field. Motor action depends on force on a current-carrying conductor in a magnetic field, explained by Fleming's left hand rule. A ceiling fan works because an electric motor rotates its blades when current passes through the coil system inside it.

3-mark answer

When current flows through the coil of a motor placed in a magnetic field, forces act on the two sides of the coil in opposite directions. These forces create a turning effect, so the coil rotates. The split-ring commutator helps keep the coil rotating in the same direction. Motors are used in fans, mixers, washing machines, and many other appliances. Motor action depends on force on a current-carrying conductor in a magnetic field, explained by Fleming's left hand rule. If a small motor coil is connected to a battery, one side of the coil moves upward and the other downward due to magnetic force. After half a turn, the commutator reverses current so the coil keeps turning. Explain working of an electric motor, label its parts, or state the role of the commutator. A common wrong answer is that the coil rotates because it is simply heated or pushed by the battery. The real cause is magnetic force on current-carrying sides of the coil.
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